Pressure indicator or recorder



L. G. P. THRING.

PRESSURE INDICATOR 0R RECORDER.

APPLICATION FILED MAR. 28,1921.

Patented Nov. 29, 1921.

3 SHEETS-SHEET I.

L. G. P. THRING.

Patented Nov. 29, 1921.

3 SHEETS-SHEET 2. "mlm Mul/H Mms.

L. G. P. THRING.

PRESSURE INDICATOR 0R RECORDER.

APPLECATION FILED MAR. 2B, 1.921.

Patented Nov. 29, 1921.

3 SHEETS-SHEET 3.

UNTD STATES PATENT GFFC.

PRESSURE INDICATOR OR RECORDER.

Specication of Letters Patent.

Patented Nov. .29, 1921.

Application led March 28, 1921. Serial No. 456,133.

To @ZZ 107mm t may concern Be it known that I, LEONARD GoDrRnY PINNEYTrume, a subject of the King of England, and residing at Cambridge, inEngland, have invented certain new and usetul Improvements in PressureIndicators or liecorders (for which I have filed application in GreatBritain under No. 32,193, of 1919, dated 23d December, 1919, in the nameot the present applicant,) of which the tollowing is a specification.

This invention relatesrto pressure indicators or recorders and has forits object to provide an apparatus particularly suited for measuring`and recording high and rapidly changing pressures, such for example, asare produced in the barrel ot a gun or a rifle when discharge takesplace, or in an internal combustion engine.

The Words indicator and cindicating to be taken to include recorder andrecordingl for the purposes of this specification. y y n i-ccording` tothis inrention the indicator comprises a pressure member subjected tothe pressure to be measuredand placed in a state oi? compressionthereby, a member placed in tension through the pressure member and adevice such as a mirror or pointer so connected to the said members asto be rotated to an extent proportional tothe sum of the compression ofthe first member and the extension of the second member' and therebycaused to indicate or recordA the magnitude of the pressure, the Wholeindicator having` a natural period of vibration which` is short incomparison with the period ot the pressure iiuctuations, so that theinstrument may be able to 'lollovv these {luctual'ious without beingthrown into a state ot vibration thereby, While each member is as tar asthe construction permits of uni- 'torni crosssection throughoutitslength.

The number otmembers, Which are subjected-either to 'tension orcompression under Vthe action ot the pressure to be measured. mav beincreased to any desired eX- tentf but' in a preferred arrangement Vtivoco-aiiial tubes ri'dly connected together at their upper ends areemployed. The inner tube constitutes a pressure member and has its lowerend closed to form a PMNs-'fm' subjected to the pressure, While theouter tube constitutes a tension member and has its lower end adjacentto this plunger and fixed to the base plate of the indicator. Slotsareprovided in the Walls or the tubes to allouv7 the indicating device tobe positioned outside the tubes.

The .indicating device preferably consists of al mirror rigidly mountedon a fiat spring or on a known spring controlled trunnion support and isprovided With an arm to which one end of a longitudinally rigidconncction is fixed. The other end of the rigid connection is fixed tothe pressure member, so that movement ot the pressure member appliestorsion to the spring' or rocks the mirror on its trunnions. i

r-in indicator in accordance with this invention may be employed toproduce either a. pressure time curve or a true indicator diagram. lnits simplest form, Where a pressure time curve onlj,T is required, asensitized sheet is moved uniformly in a direction parallel to the axisabout which the indicating,l mirror is rotated by the pressure member,for instance the sheet may be mounted on a drum rotating at a knownspeed on an axis parallel to or coincident with that of the tube.

It it is desired to produce a pressure space curve or a true indicatordiagram. the movement of the recording sheet is made proportional. tothe travel or the projectile in the bore oi a eun or to that ot a pistonin the case of an internal combustion engine. Alternatively means may beprovided for imparting a traverse motion to the indicatingr mirror. Tothis end a traverse table is conveniently employed and the flat springwhich carries the mirror is clamped to this table. rihc traverse tableis provided with steel points or the like so as to slide on the baseplate of the indicator and is held thereon by spring clips or similarmeans. It is a :o adapted to rotate through a small angle about the axisot' the pressure member, earryine' with it the indicating mirror, sothat the duration andthe magnitude of the pressure to be measured aresimultaneously indicated. In the case oi" a iii-carni the recoil isemployed to impart traverse motion to the table and mirror. .ln certaincases when the recoil is large the traverse table may bc dispensed u'ithsince the Whole indicator will be moved suiliciently to record a.complete indicator diagram.

Adjusting means are provided so that the position ot the flat spring orof the trunnion support can be adjusted before the said spring orsupport is clamped to the traverse table. Since the traverse table inits rotation carries with it the indicating mirror it is necessary thatthe rigid connection between the plunger and the mirror arm should beplaced centrally within the pressure member, and that the mirror shouldbe free to rotate about the axis of the said member. To this end therigid connection is formed into a strip so that it can twist about thisaxis in accordance with the motion of the traverse table, but it mustyet remain suiiiciently rigid longitudinally to 'transmit the motion ofthe plunger accurately to the mirror arm.

Y Mounted on the table and above the indicating mirror is a secondadjustable mirror which is not connected to the pressure member but isadapted to be traversed with the table. As the mirror is not moved bythe pressure it will reflect 'a line which is always at right angles tothe axis of the tube, and serves as a datum line whereby the indicatordiagram can be checked.

Conveniently the recoil actuated stop mechanism `employed to imparttraverse motion to the table and mirror comprises a rod or shaftconnecting a member fixed to the traverse table to a fixed supportingmember, which does not participate `in the recoil movement. The rodcarries a collar adapted to be engaged by a sleeve, fixed together withthe base plate of the indicator to the breech blockof the gun or rifle.

A simple form of high pressure indicator without a traverse table and apreferred construction provided with a traverse table, adapted for usein indicating 0r recording the pressure produced in the barrel of a gunor rifle when discharged takes place, are illustrated by way of examplein the accompanying drawings, in which- Figure l is a sectional sideelevation of a simple form of pressure indicator.

Figs. 2, 3 and 4 are respectively a sectional side elevation, a frontelevation and a plan of preferred construction.

Fig. 5 illustrates the alternative spring controlled trunnion supportfor the mirror.

Fig. 6 is a plan ofthe traverse table showing in section the recoilactuated stop mechamsm.

Figs. 7 and 8 are respectively a front elevation and a sectional sideelevation of a modified form of strut.

Fig. 9 shows a further thereof. y

Fig. l() is a longitudinal section through a modified form of theinvention which has four concentric tubes instead of two; and

Fig. ll illustrates diagrammatically a form of recording means suitablefor use with the present indicator.

f The simple form of indicator illustrated in Fig. l comprises a baseplate A into which modification is screwed or otherwise secured in somerigid manner the lower end of a tube B which projects through the baseplate at right angles thereto.l Disposed within this tube is an innertube C the ends of which are adjacent to those of the upper tube B, theupper ends of the two tubes being formed integral or connected togetherin some rigid manner. The lower end D of the inner tube is closed orformed solid so as'to constitute a plunger against which the pressureacts, and both tubes are as far as the construction permits of uniformcross section throughout their length. Thus the plunger D against whichthe pressure acts is directly supported by the tube C of uniform crosssection which is disposed within and connected to an outer tube B insuch a manner that the tube C is compressed and the tube B extended bythe pressure acting on the plunger, the movement of the plunger D beingequal to the sum of the extension and compression of the two tubes.Preferably the lower end of the outer tube B extends below the baseplate and is screwthreaded for attachment to the breech block or otherpart of the breech mechanism (not shown in the drawings) which isVsuitably bored or chambered to permit of the pressure of the gaseswithin the barrel having access to the plunger or pressure member withinthe end of the outer tube. Mounted within the inner tube C is a strut orplate E forming the longitudinally rigid connection between the plungerD and the arm F supporting the indicating mirror G. The actual form ofstrut employed and its method of attachment to the plunger and mirrorarm may vary considerably, provided that no relative movement betweenthe ends of the strut and the parts to which they are secured and noexcessive bending of the strut due to its own inertia can occur. In thepreferred forms of strut illustrated in the drawings, the upper end ofthe strut E is provided with a conically bored eye through which ispassed a light screw H with a conical head;

This screw H forms a light connection between the strut E and the mirrorarm F of such a kind as to insure a minimum moment of inertia about theaxis on which the mirror G rotates during the movement of the plunger.A. hole H. is bored inthe base plate of the indicator to permit theinsertion and tightening of this screw.

The body of the strut may be in the form of the flat plate or. stripshown in Fig. l but other forms may be employed, such for example as areshown in Figs. 7, 8 and 9. in the form shown in Figs. 7 and S, themirror arm is Ysupported at the center of the narrow strip E formedbetween two longitudinal slots E2 which are cut out of the strut- E.This narrow strip E can be made thinner than the part E3 of the strut in.which it is A resem -3' Fig. 9, in which a slot E2 is cut out from thestrut so as to leave a metal tongue EG to hold the mirror arm. The samefigures also show alternative methods of connecting the strut E to theplunger D; The strut may be. made integral with or lixed to the plunger,as is shown in Fig. l, or alternatively it may be secured to the sidesof the inner tube C, for example, by means of a screw thread as in Figs.7 and 8 or by lateral projections E5 (shown dotted in Fig. T) adapted toit into vgrooves in the side walls of the inner tube C. By means of thelast arrangement the strut may be made shorter without reducing theangle through which the mirror arm can rotate.

The walls of the inner and outer tubes B and C adjacent to the upper endof the strut E are slotted at J to permit theV supporting frame or arm Fof the mirror G to be connected to the strut, the mirror being carriedoutside the tubes; The indicating mirror G is thus connected to theplunger D in such a way that relative movementbetween the two ends ofthe tubes B and C causes the mirror to rotate about an axisperpendicular to that of the tubes. y

To cont-rol the movement of the mirror G about this axis it is rigidlymounted on a flat transverse spring lx the ends of which, in the simpleform7 are clamped to the base plate A of the indicator by means of ascrew K. To insure greater rigidity against bending in the plane of thespring the ends may be encastred by duplicating the screw K at eitherend or in any other manner. Alternatively the mirror may be mounted ontrunnions L and M as shown in Fig. 5, the trunnion L having a plainbearing in a iixed support, while the other trunnion M is supported in aiat spring which prevents any play in the bearing, the two trunnionsupports in the simple form' being respectively carried by and clampedto the base plate A.

In operation the simple form of indicator above described is screwed tothe breech bloc-k of the gun or rifle in such a manner that the gasesgenerated by the explo-sion exert pressure on the plunger B andconsequently compress .the tube and extend the tube B so that the strutE moves upward and b v applying torsion to the spring' K rotates themirror Gr. The mirror G reflects a spot of light on to a sensitizedsheet moved parallel to the axis of rotation of the mirror, and apressure time curve or a pressure space curve is produced on the: sheetaccording as the sheet is moved uniformly or proportionally to thetravel of the bullet in the barrel.

l/Vhere the recoil is small this simple form of indicator cannotconveniently produce a true indicator diagram or pressure space curvewithout' the employment of some fairly complicated mechanism to providefor the necessary variable speed of movement of the sensitized sheet. Toobviate this, the preferred form of indicator illustrated in Figs. 2, 3and 4e is provided with means to give to the indicating mirror atraverse movement actuated by the recoil and proportional to the travelof the bullet or shell in the barrel.

This preferred construction incorporates all the parts described withreference to the simple construction illustrated in Fig.

l, with a slight variation lin their arrangement hereinafter described.but it also includes ai traverse table N supported on three steel pointsU or the like on the base plate A. This traverse table N is rotatableabout the axis of the tubes B and C and the i outer tube B has its wallsslightly thickened to support the bearings on the traverse table. Thethree steel points O are held in contact with the upper surface of thebase plate A by spring pressure members P which may be of any suitableform and are designed and arranged to permit slight rotary movement ofthe table. their lower ends bearing in holes or pockets in the table.The iiat transverse spring K is, in this preferred construction, clampednot to the base plate A but to two supporting shoulders t.) fixed to thetraverse table. kdjusting screws R are provided whe the position of theflat spring K and the r; irror Gr which it carries may be adjusted tobring the mirror into a suitable initial position before the ends of thespring' are clamped in position on the shoulders Q by' the scr s K.Alternatively the trunnion support illustrated in Fig. 5 may besubstituted for the flat spring K in this construction also.

In this preferred construction the strut E is placed centrally withinthe pressur tube C and is in the form of a metal strip so that it cantwist about the axis of the tube and yield to the torsional forceproduced in it by the traversing of the mirror G, but it must still besuihcient-ly rigid longitudinally to transmit the motion of the plungerD accurately to the mirror arm F. Thus there is no lost motion betweenthe pressure member and the indicating mirror.

The auxiliary mirror Z is adjustably mounted on the traverse table N soas to provide a datum line on the sensitized sheet whereby the indicatordiagram can be checked.

Fig. 6 illustrates a preferred method by which the'recoil is made toactuate the traversing table. The inner end of a rod or shaft S isformed into a strip and engages with a member T fix-ed to the traversetable N. The outer end of the rod S is carried in a bearing' in asupporting bracket or standard U fixed to the ground or otherwise heldstationary so that it does not participate in the ses 1,398,608

recoil movement. A collar V vfixed to the rod S is held away from thefixed supporting member U by a spring W. An arm or member ending inasleeve X which slides on the rod S and engages with the 'collar Vduring the recoil, is fixed to the base plate A of the indicator andthereby also to the breech block or other recoiling portion of the gunor rifle. An adjusting nut Y is provided so that the'elfective length ofthe rod S may be varied.

After iiring, the member X is forced by the recoil to slide along therod Sand after a short interval it engages the collar V. Until thisengagement takes place the rod S and consequently also the slottedmember T remain stationary, but the base plate A has also moved with therecoil and the traverse table N has therefore moved relative to the baseplate. After the member X has engaged wth the collar V however, the rodS movesl with the base plate A until the end of the recoil, and nofurther relative motion can occur between the traverse table N and thebase plate A.

Any number of pressure and tension members may be employed and in Fig.10 a modified form of indicator is shown having two pressure members andtwo tension members. The construction of this form is the same as thatshown in Figs. 2, 3 and 4 with the exception that instead of one innertube Q and one outer tube B, two tubes C and C2 are shown which aresubjected to compression and two tubes B and B2 which are subjected totension. The innermost tube C2 is closed at its lower end to form aplunger D and the outermost tube B2 is fixed to the plate A of theindicator.

A simple form of recording means is illustrated diagrammatically by wayof example in Fig. 1l and comprises a casing Z3 having an opening VZ4adapted to register with an opening Z2 in a casing Z surrounding theindicatorand mounted on the base plate thereof, a point source of lightZ5 and a sensitive sheet. Z6. The source of light is so arranged thatthe rays therefrom impinge both on the indicating mirror G and theauxiliary mirror Z whence they are reflected to the sensitive sheet Z6.Y

ln operation the indicator is mounted on the breech block or otherrecoiling portion of the gun or rifle and the whole apparatus isinclosedwithin any suitable light proof casing, the light from a pointsource being reflected from the mirror on to a suitably positionedsensitized sheet. lf the indicator is used for testing the pressure in arifle barrel, the riiie is conveniently clamped in a vise mountedon aslide. The gases which are generated when discharge takes place arecaused to act upon the closed end or plunger D of the inner tube C,whereupon relative movement between the lower ends of the tubes B and Cis transmitted by the strut E to the indicating mirror Gr, causing thismirror to rotate about an axis perpendicular to the axis of the tube Band so applying torsion to the flat spring K on which it is mounted.

Simultaneously the recoil, through the stop mechanism above described,causes the traverse table N to rotate the indicating mirror G about theaxis of the tube B, thereby twisting the 'shank of the strut E. Thepoint of light reflected by this mirror G on to the sensitized sheet isthus caused to trace a true indicator diagram, in which the verticalcoordinate represents pressure and the horizontal cordinate the lengthof the recoil.

The point of light reflected by the second mirror on the traversingtable will serve to indicate in the lirst instance that the instrumentis properly adjusted and not subjected to excessive vibration whilefurther the straight line which it will produce on the sensitized sheetwill serve as a datum line from which the indicator diagram can bechecked.

It will be appreciated that the instrument described above is merely oneform of ,the invention as applied to a particular purpose, namelymeasuring and recording the pressures produced in the barrel of a gun orrifleiwhen discharge takes place. Obviously the construction of theinstrument and its general arrangement will be modified to suit varyingcircumstances, the actual indicating member in some cases being in theform of a pointer if found convenient. Further the particular form ofpressure member employed can be varied more especially in indicators forinternal combustion engines or where a pointer is employed. For instancethree concentric tubes may be used of which two arev in compression andone in tension.

The pressure and tension members may be constructed out of any suitablematerial, Y

which has a large amount of resilience and a certain amount oftoughness, such for example, asl various grades of high carbon steel,vanadium steel or nickel-chrome steel.v

What I claim as my invention and desire to secure byLetters Patent is l.In a iiuid pressure indicator, in combination, an elongatedsubstantially straight elastic member, one end of which is supportedandthe other end of which is free and adapted to be subjected topressure to strain the member in the direction of its length, and adevice associated with said member for indicating the amountV of itsdeformation.

2. In a Huid pressure indicator, in combination7 an elongatedsubstantially straight elastic member, one end of which is supported andthe other end of which is free and adapted to be subjected to pressureto strain the member in the direction of its length, and a mirrorconnected to the free end ot said member to indicate the amount of itsdeformation.

3. In a. fluid pressure indicator, in combination, an elongatedsubstantially straight elastic member, one end of which is supported andthe other end of which is free and adapted to be subjected to pressureto strain the member in the direction oi' its length, and an indicatingelement mounted on a relatively fixed base and connected t-o the freeend oit said member, to indicate the amount of its deformation.

4. In a fluid pressure indicator, in combination, an elongatedsubstantially straight elastic member', one end of Which is supportedand the other end of which is tree and adapted to be subjected topressure to strain the member in the direction of its length, arelatively fixed base, and a mirror pivotally supported on the -base andcon-A nected to the free end of the elastic member, for indicating theamount ot deformation.

5. In an indicator of the type described, in combination, tivo elasticmembers secured together at one point, one of said members beingsupported on a relatively fixed base and the other member having aportion adapted to be subjected to pressure so that both of said membersare strained thereby and a device for indicating the total of the addedstrains of both of said members.

G. In an indicator for high pressures, the combination of a pressuremember, a tension member coacting with the pressure member, anindicating device, and means connecting the indicating device to thesaid members, such means being adapted to move the indicating device toan extent proportional to the sum ot the compression ot the pressuremember and the extension of the tension member.

7. In an indicator for high pressures, the combination of a pressuremember, a tension member coacting with the pressure member, anindicating device, means connecting the indicating device to the saidmembers, such means being adapted to move the indicating device to anextent proportional to the sum ot the compression ot the pressure memberand the extension ot the tension member thus giving an indication ci themagnitude of the pressure, the ivhole apparatus having a natural periodof vibration Which is short in comparison with that otl the pressureiiuctuations.

S. An indica-tor Of high pressures comprising a plurality of members oneot which is subjected to the pressure to be measured, a tension membercoacting with the pressure member so that it ivill be in a state oftension vwhen the pressure member is Compressed`v an indica-ting device,and means connecting the indicating device to the Said members, suchmeans being adapted to move jected to the pressure to be measured, suchtube constituting a pressure member, an outer tube coaxial with andrigidly connected at its upper end to the inner tube and having itslower end adjacent to the plunger and secured to the base plate, suchouter tube constituting a tension member, a rotatable indicating deviceand means connecting the indicating device to the plunger, as set forth.

10. An indicator for high pressures comprising a base plate, an innertube having its lower end closed to form a plunger subjected to thepressure to be measured, such tube constituting a pressure member, anouter tube coaxial with and rigidly connected at its upper end to thetube and having its loiver end adjacent to the plunger and secured tothe base plate, such outer tube constituting a tension member, arotatable indicating device, means connecting the indicating device tothe plunger, such means being adapted to rotate the indicating device toan "extent proportional to the sum of the compression ot the inner tubeand the extension of the outer tube, the whole apparatus having anatural period of vibration which is short in comparison with that otthe pressure iluctuations.

ll. An indicator for high pressures comprising a base pla-te, an innertube having its loiver end closed to Jform a plunger subjected to thepressure to be measured, such tube constituting a pressure member, anouter tube coaxial with and rigidly connected at its upper end to theinner tube and having its loiver end adjacent to the plunger and securedto the base plate, such outer tube constituting a tension member, arotatable indicating device, slots in the Walls ot the tubes to permitthe indicating device to be positioned outside the tubes, and meansconnecting` the indicating device to the plunger, such means beingadapted to rotate the indicating device to an extent proportional to thesum of the compression of the inner tube and the extension of the outertube as set forth.

12. In an indicator for high pressures, the combination of a pressuremember adapted to be subjected to the pressure to be measured, a tensionmember coacting l@ pressure as set forth.

13. An indicator for high pressures comprising a base plate, an innertube having its lower end closed to form a plunger subjected to thepressure to be measured, such tube constituting a pressure member, anouter tube coaxial with and rigidly connected at its upper end to theinner tube and having its lower end adjacent to the plunger and securedto the base plate, such outer tube constituting a tension member sothat` it will be in a state of tension When the inner tube iscompressed, a rotatable indicating mirror, and means connecting theindicating mirror to the plunger, such means being adapted to rotate theindicating mirror to an extent proportional to the sum ofthe compressionof the inner tube and the eX- tension of the outer tube as set forth.

14. In an indicator for high pressures, the combination of a pressuremember adapted to be subjected to the pressure to be measured, a tensionmember vcoacting with the pressure member so that it will be in a stateof tension when the pressure member is compressed, a rotatableindicating mirror, a flat spring upon which the mirror is rigidlymounted and which serves as a pivot about which the mirror can rotate,and means connecting the indicating mirror to the said members, suchmeans being adapted to rotate the indicating mirror to an extentproportional to the sumvof the compression of the'pressure member andthe extension of the tension member thus giving an indication of themagnitude of the pressure as set forth.

15. An indicator for high pressures comprising a base plate, an innertube having its lower end closed to form a plunger subjected to thepressure to be measured, such tube constituting a pressure member, anouter tube coaxial With and rigidly connected at its upper end to theinner tube and having its lower end adjacent to the plunger and securedto, the base plate, such outer tube constituting a tension member sothat it will be in a state of tension when the inner tube is compressed,a rotatable indicating mirror, a flat spring on which the mirror isrigidly mounted and which serves as a pivot about which the mirror canrotate, and means connecting the indicating mirror to theplunger, suchmeans being adapted to rotate the indicating mirror to an extentproportional to the sum of the compression the combination of a pressuremember adapted to be subjected' to the pressure to be measured, atension member coacting With the pressure member so that it will be in astate of tension when the pressure member is compressed, a rotatableindicating mirror, a flat spring upon which the mirror is rigidlymounted and which serves as a pivot about Which the mirror can rotate,an arm fixed to the mirror, and a longitudinal rigid connection betweenthe pressure member and the mirror arm of such a kind that movement ofthe pressure member applies torsion to the flat springend rotates themirror thus giving an indication of the magnitude of the pressure as setforth.

17. In an indicator for high pressures, the combination of a pressuremember adapted to be subjected to the pressure to be measured, a tensionmember coacting with the pressure member so that it Will be in a stateof tension when the pressure member is compressed, a. base plate, arotatable indicating device, a traverse table adapted to slide onthebase plate of the indicator and to rotate thereon through'a small angleabout the axis of the pressure member, a support for the indicatingdevice clamped to shoulders on the said table, means con necting theindicating device to the said members, and means for simultaneouslyrotating the traverse table and the indicating device so that theduration and the magnitude of the pressure are simultaneously in-Vdicated as set forth.

18. In an indicator for high pressures, the combination of a pressuremember adapted to be subjected to the pressure. to be measured, atension member c'oacting with the pressure member so that it Will be ina state of tension When'the pressure member is compressed, abase plate,a rotatable indicating device, a traverse table adapted to slide on thebase plate of the indicator' and to rotate thereon through a small angleabout the axis of the pressure member, a support for the indicatingdevice clamped to shoulders on the said table, means connecting theindicating device to the said members, means lfor simultaneouslyrotating the traverse table and thevindicating device so that theduration and the magnitude of the pressure are simultaneously indicated.

19. An indicator for high'pressures comprising a base plate, an innertube having its lower end closed to form aV plunger subjected to thepressure to be measured, such tube constituting a pressure member, anouter tube coaxial with and rigidly connected at its upper `end totheinner tube and having its lower end adjacent to the plunger andsecured to the base plate, such outer tube constituting' a tensionmember so that it will be in a state ot tension when the inner tube iscompressed, a rotatable indicating device, a traverse table adapted toslide on the base plate or' the indicator and to rotate thereon througha small angle about the axis of the tubes, a support for the indicatingdevice clamped to shoulders on the said table, means connecting theindicating device to the plunger, and means for simultaneously rotatingthe traverse table and the indicating device so that the duration andmagnitude of the pressure are simultaneously indicated asset forth.

20. An indicator for high pressures comprising a base plate, an innertube Yhaving its lower end closed to form a plunger subjected to thepressure to be measured, such tube constituting a pressure member, anouter tube coaxial With and rigidly connected at its upper end to theinner tube and having its lower end adjacent to the plunger and securedto the base plate, such outer tube constituting a tension member so thatit Will be in a state of tension when the inner tube is compressed, arotatable indicating mirror, a traverse table adapted to slide on thebase plate of the indicator and to rotate thereon through a small angleabout the axis of the tubes, a flat spring upon Which the mirror isrigidly mounted and which is clamped to shoulders on the said table thusserving as a pivot about Which the mirror can rotate, means connectingthe indicating mirror to the plunger, and means tor simultaneouslyrotating` the traverse table and the indicating mirror so that theduration and magnitude oi:- the pressure are simultaneously indicated asset forth.

2l. In an indicator for high pressures the combination of a pressuremember adapted to be subjected to the .pressure to be measured, atension member coacting with the pressure member so that it will be inastate of tension when the pressure member is compressed, a base plate, arotatable indicating mirror, a traverse table adapted to slide on thebase plate of the indicator and to rotate thereon through a small angleabout the axis of the pressure member, a flat spring upon which themirror is rigidly mounted and which is clamped to shoulders on the saidtable thus serving as a pivot about which the mirror can rotate, an armfixed to the mirror, a longitudinally rigid connection betiveen thepressure member andthe mirror arm, means for simultaneously rotating thetraverse table and the indicating mirror so that the duration andmagnitude of the pressure are simultaneously indicated, thelongitudinally rigid connection Vbeing placed substantially centrallyWithin the pressure member and formed as a strip so that it can twistthrough a small angle in accordance with the motion of the traversetable but yet remain sufficiently rigid longitudinally to transmit themotion oit' the pressure member accurately to the indicating mirror asset forth.

22. An indicator for high pressures comprising a base plate, an innertube having its lower end closed to form a plunger subjected to thepressure to be measured, such tube constituting a pressure member andbeing placed in a state of compression when the pressure acts, an outertube coaxial ivith and rigidly connected at its upper end to the innertube and havin@- its loiver end adjacent to theplunger and secured tothe base plate, such outer tube constituting a tension member so that itwill be in a state of tension When the inner tube is compressed, arotatable indicating device, a traverse table adapted to slide on thebase plate of the indicator and to rotate thereon through a small angleabout the axis of the tube, spring pressure members adapted to hold thetraverse table on to the base plate, a support :tor the indicatingdevice clamped to shoulders on the said table, means connecting theindicating device to the plunger, and means for simultaneously rot-atingthe traverse table and the indicating device so that the duration andmagnitude oi the pressure are simultaneously indicated as set forth,

23. An indicator for high pressures comprising a base plate, an innertube having its lower end closed to `form a plunger subjected to thepressure to b e measured, such tube constituting a pressure member, anouter tube coaxial with and rigidly connected at its upper end to theinner tube and having its lower end adjacent to the plunger and securedto the base plate, such outer tube constituting a tension member so thatit Will be in a state of tension when the inner tube is compressed, arotatable indicating mirror, a traverse table adapted to slide on thebase plate of the indicator and to rotate thereon through a small angleabout the axis of the tubes, a support for the in dicating mirrorclamped to shoulders on the said table, means connecting the indieatingmirror to the plunger, means for simultaneously rotating the traversetable and the indicating mirror so that the duration and magnitude ofthe pressure are simultaneously indicated, means for recording theindications given by the indicating mirror7 and an auxiliary mirroradjustably mounted on the traverse 'table so as to indicate the motionthereof and to provide a datum line on the r cord of the indicationwhereby the pressure diagram may be checked as set forth.

24. In an indicator for high pressures, the combination of a pressuremember adapted to be subjected to the pressure to be measured, a tensionmember coacting with the pressure member so that it will be in a stateof tension when the pressure member is compressed, a base plate, arotatable indicating mirror, a traverse table adapted t0 slide on thebase plate of the indicator and to rotate thereon through a small angleabout the axis of the pressure member, a support for the indicatingmirror clamped to shoulders on the said table, means connecting theindicating mirror to the said members, means for simultaneously7rotating its traverse table and the indicating mirror so that theduration and the magnitude of the pressure are simultaneously indicated,means for recording the indications given by the indicating mirror, andan auxiliary mirror adjustably mounted on the traverse table so as toindicate the motion thereof and to provide a datum Vline on the recordof the indication whereby the pressure diagram may be checked as setforth.

25. In a pressure indicator for guns, rifles or the like, thecombination of a pressure member adapted to be subjected to the pressureto be measured, a tension membe-r coactinowith the pressure member sothat it will be in a state of tension when the pressure member iscompressed, a base plate, a rotatable indicating device, a traversetable adapted to slide on the base plate of the indicator and to rotatethereon through a small angle about the axis of the pressure member, asupport for the indicating device clamped to shoulders on the saidtable, means connecting the indicating device to the said members, meansto rotate the indi- Veating device, and a recoil actuated stop mechanismadapted to rotate the traversel table so that the duration and themagnitude of the pressure are simultaneously indicated as set forth.

26. In a pressure indicator for guns, rifle-s or the like, thecombination of a pressure member adapted to be subjected to the pressureto be measured and placed in a state of compression thereby, a tensionmember coacting with the pressure member so that it Will be in a stateof tension when the pressure member is compressed, a'base plate, arotatable indicating` device, a traverse table adapted to slide on thebase plate of the indicator and to rotate thereon through a small angleabout the axis of the pressure member', a support for the indicatingdevice clamped to shoulders on the said table,means connecting theindicating device to the said members, means to rotate the indicatingdevice, and a recoil actuated stop mechanismV adapted to rotate thetraverse table so that the duration and the magnitude of the pressureare simultaneously indicatedo 27. 'A pressure indicator for guns, riflesor the like comprising a base plate, an inner tube having its lower endclosed to form a plunger subjected to the pressure to be measured, suchtube constituting a pressure member and being placed in a state ofcompression When the pressure acts, an outer tube coaxial With andrigidly connected at its upper end to the inner tube and havingitsrlower end adjacent to the plunger and secured to the base plate,such outer tube constituting a tension member so that it will be in a.state of tension when the inner tube is compressed, a rotatableindicating device, a traverse table adapted to slide on the base plateof the indicator and to rotate thereonV through a small angle about theaxis of the tubes, a support for the indicating device clamped toshoulders on the said table, means connecting the indicating device totheplunger, means to rotate the indicating device, and a recoil actuatedstop mechanism adapted to rotate the traverse table so that the durationand the magnitude of the pressure are simultaneously indicated as setforth.

28. An indicator for high pressures comprising a plurality of membersone of which is subjected to the pressure to be measured, a tensionmember coacting with the pressure members, an indicating device, andmeans connecting the indicating device to the said members, said meansbeing adapted to move the indicating device to an extent proportional tothe sum of the compression of the 100 pressure members and the extensionof the tension member, the Whole apparatus having a natural period ofvibration which is short in comparison with that of the pressurefluctuations and each memberl being substan- 105 tially of uniform crosssection throughout its length as set forth.

29. n indicator for high pressures comprising a plurality of pressuremembers one of which is subjected to the pressure to 110 be measured, aplurality of tension members coacting with the pressure members, anindicating device, and means connecting the indicating device t0 thesaid members, said means being adapted to move the indicating 115 deviceto an extent proportional to the sum of the compression of the pressuremembers and the extension of the tension members, the whole apparatushaving a. natural period of vibration, which is short in comparison to120 that of the pressure fluctuations and each member beingsubstantially of uniform cross section throughout its length.

30. An indicator for high pressures comprising a base plate, an innertube having 1725V and secured to the base plate, said outertubeconstituting a tension member, a rotatably indicating mirror, meansconnecting the indicating mirror to the plunver, such mea-ns beingadapted to rotate the in icating mirror to an extent proportional to thesum of the compression of the inner tube and the extension of the outertube, and means for recording the indications given by the indicatingmirror as set forth.

3l. In a iiuid pressure indicator, in combination, a substantiallystraight elastic member adapted to be strained in the direction of itslength when subjected to pressure, a device associated therewith forindicating the amount of deformation, and means cooperating with saiddevice for recording deformations indicated thereby.

32. An indicator for high pressures comprising a base plate, an innertube having its lower end closed to form a plunger subjected to thepressure to be measured, an

outer tube coaxial with and rigidly connected at its upper end to theinner tube and having its lower end adjacent to the plunger and securedto the base plate, such outer tube constituting a tension member, arotatable indicating device, a traverse table adapted to slide on thebase plate of the indicator and to rotate thereon through a small angleabout the axis of the tubes, the spring pressure members adapted to holdthe traverse table on to the base plate, a sup-

